When you say split, what do you mean, did you "shift+D" to split the layer? If you did that, you can move the mouse over the layer end, grab it and extend it back out to it's original length. Or you could press "alt+[" to move the head or "alt+]" the tail of the layer back out. But if it's split it can't be recombined with itself in the timeline.l.
If that's not what you are trying to accomplish, perhaps some screens shots and a more detailed explanation of what you did and want to do will help us diagnose the problem and come up with some suggestions.
Johnny Cuevas, Editor
"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.